Flashcards
Lecture 2- Introduction to colour flow imaging and spectral doppler ultrasound
Flashcards do conjunto (41)
- 1What does colour flow imaging show?-The mean velocity of flow in relation to the ultrasound beam
-Mean velocity means mean speed and mean direction - 2Flow towards the transducer is displayed as......red
- 3Red on the colour flow displays......movement towards the transducer
- 4Blue on the colour flow displays......movement away from the transducer
- 5Flow away from the transducer is displayed as......blue
- 6The shade of colour depends on the _a)_. Since velocity is composed of _b)_ and _c)_, the shade of the image depends on the _d)_ and _e)_a) velocity
b) speed
c) direction
d) speed of flow
e) direction of flow relative to the ultrasound beam i.e the angle of insonation - 7E.g If 2 blood cells were carrying blood away from the transducer AT THE SAME SPEED, however one was parallel to the ultrasound and one was at a 45 degree angle, which vessel will appear with a deeper blueThe vessel at a 45 degree angle because this vessel only displays a percentage of it's true velocity, therefore the displayed colour represents a lower velocity than its actual velocity
- 8e.g if 2 blood vessels, parallel to the ultrasound beam, were carrying blood away from the transducer, but at differing speeds, which vessel will appear a brighter blueThe vessel carrying blood at a faster speed
- 9The brighter the shade on the colour flow image, the _a)_ and the _b)_a) faster the speed of flow
b) more aligned the direction of flow is to the ultrasound beam - 10What is the angle of insonation?The angle between the path of the ultrasound beam and the path of blood flow
- 11The angle of insonation is used to measure how......aligned the ultrasound beam is to the blood flow
- 12What is the doppler effect?A change in received frequency (or wavelength) compared to the transmitted frequency, which occurs due to the relative motion between the source and the transducer ie as they move away or towards the transducer
- 13What is the term given to when there is a change in received frequency (or wavelength) compared to the transmitted frequency, which occurs due to the relative motion between the source and the transducerdoppler effect
- 14*Doppler effect* The transmitted ultrasound is _a)_ from the moving blood cells. As the blood cells move, the _b)_ of the received echo _c)_. The change in the received frequency from the transmitted frequency is known as the _d)_. This gives us the _e)_ of blood flowa) backscattered
b) frequency
c) changes
d) doppler shift frequency
e) velocity (speed of flow and direction of flow) - 15Each scan line on an ultrasound image can be broken down into _a)_. In colour flow imaging, the _b)_ is displayed as a colour. When the the mean velocityof a sample volume is plotted against time, it gives a _c)_a) several sample volumes
b) mean velocity
c) spectral doppler - 16What is a spectral dopplerWhen a single beam is used and the mean velocity of a single sample volume is plotted against time. This is used to quantify blood flow and resistance
- 17TRUE OR FALSE: Colour flow imaging has a lower frame rate than B-mode imagingTrue
- 18TRUE OR FALSE: Colour flow imaging has a higher frame rate than B-mode imagingFalse
- 19Linear transducers are able to _a)_ the colour flow beam to achieve _b)_. Therefore, allowing the angle of the B-mode scan lines to _c)_ from the angle of the colour flow scan linesa) steer
b) an angle of insonation of choice
c) differ - 20Because we can't steer the colour flow beam on phased array transducers, how do we overcome this obstacle?The transducer is tilted manually
- 21TRUE OR FALSE: The angle of the colour flow beam and B-mode scan lines can differ in phased array transducersFalse. This can only be done for linear transducers
- 22Good colour flow images have good _a)_ and good _b)_a) filling
b) contrast ( range of velocities showing) - 23We can optimise colour flow images by......altering the angle of insonation
- 24What assumption does the machine make in terms of colour flow imaging?The machine assumes the angle of insonation is 0, therefore the colour presented is based on the machine assuming the angle of insonation is 0
- 25Cos (0)= _a)_ = _b)_% of true velocitya) 1
b) 100 - 26Cos (90)= _a)_ = _b)_% of true velocitya) 0
b) 0 - 27Cos (60)= _a)_ = _b)_% of true velocitya) 0.5
b) 50 - 28Cos (45)= _a)_ = _b)_% of true velocitya) 0.7
b) 70 - 29In colour flow imaging, the value of Cos(α) gives the......percentage of the true velocity displayed
- 30When blood flow is parallel to the colour flow beam, how much of the true velocity is presented?α= 0
cosα= 1
therefore 100% of the true value is presented - 31When blood flow is perpendicular to the colour flow beam, how much of the true velocity is presented?α= 90
cosα= 0
Therefore 0% of the true velocity is presented, which means no velocity is shown - 32When blood flow is 45 degrees to the colour flow beam, how much of the true velocity is presented?α=45
cosα= 0.7
Therefore 70% of the true velocity is displayed - 33When blood flow is 60 degrees to the colour flow beam, how much of the true velocity is presented?α=60
cosα= 0.5
Therefore 50% of the true velocity is displayed - 34When the angle is between 0-90 degrees, as the angle of insonation increases, the % of error _a)_a) increases (ie less of the true velocity is displayed)
- 35When the angle is between 90-180 degrees, as the angle of insonation increases, the % of error _a)_a) decreases (ie the closer the value is to the true velocity)
- 36If cosα= -ve what does this suggest?The direction of flow is away from the transducer because α>90
- 37What angle of insonation displays 50% of the true velocity?cosα= 0.5 or-0.5
therefore α= 60 or 120 degrees - 38What angle of insonation displays 70% of the true velocity?cosα= 0.7 or -0.7
therefore α= 45 or 135 degrees - 39In clinical settings, we aim for an angle of insonation of _a)_ because it gives the best blood flow detection after taking into account _b)_a) 0-60 or 120-180 degrees
b) physical restrictions - 40Work out the true velocity of blood in this image*The displayed velocity is approx 20m/s
*The blood is flowing towards the transducer, therefore the approximate angle of insonation is 45 degrees
*Cos(45)= 0.7, therefore 70% of true velocity is being displayed
* 20m/s is only 70% of true velocity
therefore 1%=20/70
Therefore 100%= (20/70)x 100= 28.6m/s - 41When using an angle correction cursor in spectral doppler, the smaller the angle of insonation, the _a)_sensitive it is to errora) less (because you can afford to be +/-5 degrees, without creating a lot of error)
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- Masters Physics FlashCards sobre Lecture 2- Introduction to colour flow imaging and spectral doppler ultrasound, criado por Rosh Wood em 18-10-2019.
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- Rosh Wood
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